nlohmann/detail/string_concat.hpp

0001 //     __ _____ _____ _____
0002 //  __|  |   __|     |   | |  JSON for Modern C++
0003 // |  |  |__   |  |  | | | |  version 3.11.2
0004 // |_____|_____|_____|_|___|  https://github.com/nlohmann/json
0005 //
0006 // SPDX-FileCopyrightText: 2013-2022 Niels Lohmann <https://nlohmann.me>
0007 // SPDX-License-Identifier: MIT
0008
0009 #pragma once
0010
0011 #include <cstring> // strlen
0012 #include <string> // string
0013 #include <utility> // forward
0014
0015 #include <nlohmann/detail/meta/cpp_future.hpp>
0016 #include <nlohmann/detail/meta/detected.hpp>
0017
0018 NLOHMANN_JSON_NAMESPACE_BEGIN
0019 namespace detail
0020 {
0021
0022 inline std::size_t concat_length()
0023 {
0024     return 0;
0025 }
0026
0027 template<typename... Args>
0028 inline std::size_t concat_length(const char* cstr, Args&& ... rest);
0029
0030 template<typename StringType, typename... Args>
0031 inline std::size_t concat_length(const StringType& str, Args&& ... rest);
0032
0033 template<typename... Args>
0034 inline std::size_t concat_length(const char /*c*/, Args&& ... rest)
0035 {
0036     return 1 + concat_length(std::forward<Args>(rest)...);
0037 }
0038
0039 template<typename... Args>
0040 inline std::size_t concat_length(const char* cstr, Args&& ... rest)
0041 {
0042     // cppcheck-suppress ignoredReturnValue
0043     return ::strlen(cstr) + concat_length(std::forward<Args>(rest)...);
0044 }
0045
0046 template<typename StringType, typename... Args>
0047 inline std::size_t concat_length(const StringType& str, Args&& ... rest)
0048 {
0049     return str.size() + concat_length(std::forward<Args>(rest)...);
0050 }
0051
0052 template<typename OutStringType>
0053 inline void concat_into(OutStringType& /*out*/)
0054 {}
0055
0056 template<typename StringType, typename Arg>
0057 using string_can_append = decltype(std::declval<StringType&>().append(std::declval < Arg && > ()));
0058
0059 template<typename StringType, typename Arg>
0060 using detect_string_can_append = is_detected<string_can_append, StringType, Arg>;
0061
0062 template<typename StringType, typename Arg>
0063 using string_can_append_op = decltype(std::declval<StringType&>() += std::declval < Arg && > ());
0064
0065 template<typename StringType, typename Arg>
0066 using detect_string_can_append_op = is_detected<string_can_append_op, StringType, Arg>;
0067
0068 template<typename StringType, typename Arg>
0069 using string_can_append_iter = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().begin(), std::declval<const Arg&>().end()));
0070
0071 template<typename StringType, typename Arg>
0072 using detect_string_can_append_iter = is_detected<string_can_append_iter, StringType, Arg>;
0073
0074 template<typename StringType, typename Arg>
0075 using string_can_append_data = decltype(std::declval<StringType&>().append(std::declval<const Arg&>().data(), std::declval<const Arg&>().size()));
0076
0077 template<typename StringType, typename Arg>
0078 using detect_string_can_append_data = is_detected<string_can_append_data, StringType, Arg>;
0079
0080 template < typename OutStringType, typename Arg, typename... Args,
0081            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0082                          && detect_string_can_append_op<OutStringType, Arg>::value, int > = 0 >
0083 inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest);
0084
0085 template < typename OutStringType, typename Arg, typename... Args,
0086            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0087                          && !detect_string_can_append_op<OutStringType, Arg>::value
0088                          && detect_string_can_append_iter<OutStringType, Arg>::value, int > = 0 >
0089 inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
0090
0091 template < typename OutStringType, typename Arg, typename... Args,
0092            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0093                          && !detect_string_can_append_op<OutStringType, Arg>::value
0094                          && !detect_string_can_append_iter<OutStringType, Arg>::value
0095                          && detect_string_can_append_data<OutStringType, Arg>::value, int > = 0 >
0096 inline void concat_into(OutStringType& out, const Arg& arg, Args && ... rest);
0097
0098 template<typename OutStringType, typename Arg, typename... Args,
0099          enable_if_t<detect_string_can_append<OutStringType, Arg>::value, int> = 0>
0100 inline void concat_into(OutStringType& out, Arg && arg, Args && ... rest)
0101 {
0102     out.append(std::forward<Arg>(arg));
0103     concat_into(out, std::forward<Args>(rest)...);
0104 }
0105
0106 template < typename OutStringType, typename Arg, typename... Args,
0107            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0108                          && detect_string_can_append_op<OutStringType, Arg>::value, int > >
0109 inline void concat_into(OutStringType& out, Arg&& arg, Args&& ... rest)
0110 {
0111     out += std::forward<Arg>(arg);
0112     concat_into(out, std::forward<Args>(rest)...);
0113 }
0114
0115 template < typename OutStringType, typename Arg, typename... Args,
0116            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0117                          && !detect_string_can_append_op<OutStringType, Arg>::value
0118                          && detect_string_can_append_iter<OutStringType, Arg>::value, int > >
0119 inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
0120 {
0121     out.append(arg.begin(), arg.end());
0122     concat_into(out, std::forward<Args>(rest)...);
0123 }
0124
0125 template < typename OutStringType, typename Arg, typename... Args,
0126            enable_if_t < !detect_string_can_append<OutStringType, Arg>::value
0127                          && !detect_string_can_append_op<OutStringType, Arg>::value
0128                          && !detect_string_can_append_iter<OutStringType, Arg>::value
0129                          && detect_string_can_append_data<OutStringType, Arg>::value, int > >
0130 inline void concat_into(OutStringType& out, const Arg& arg, Args&& ... rest)
0131 {
0132     out.append(arg.data(), arg.size());
0133     concat_into(out, std::forward<Args>(rest)...);
0134 }
0135
0136 template<typename OutStringType = std::string, typename... Args>
0137 inline OutStringType concat(Args && ... args)
0138 {
0139     OutStringType str;
0140     str.reserve(concat_length(std::forward<Args>(args)...));
0141     concat_into(str, std::forward<Args>(args)...);
0142     return str;
0143 }
0144
0145 }  // namespace detail
0146 NLOHMANN_JSON_NAMESPACE_END